Market needs such as high performance and miniaturization has resulted in the need for more integrated semiconductor elements on microelectronic devices. For example, a high-level planarization technique for forming a finer circuit pattern is necessary, wherein a CMP step of polishing a wafer surface using a polishing slurry (hereinafter, abbreviated to a CMP slurry) containing particulates of alumina or silica is effectuated.
In this CMP step, however, various substances remain on the device after polishing, for example: polishing particulates such as alumina and silica in the CMP slurry (hereinafter, abrasive grains), iron nitrate aqueous solutions added to accelerate polishing, anticorrosive added to suppress corrosion of a metal, and residues of a polished metal wiring and zinc and magnesium metals used on a side of said metal wiring. These residues can have an adverse effect on electrical properties of the semiconductor such as shorting. Accordingly, it is necessary to remove these residues prior to proceeding to the next manufacturing step.
In the related art for tungsten CMP, post-CMP methods typically use an ammonia and hydrogen peroxide aqueous solution or a hydrochloric acid and hydrogen peroxide aqueous solution in combination with a diluted hydrofluoric acid aqueous solution. In such a method, however, the wiring metal can be substantially corroded. Accordingly, the method cannot be applied to modern microelectronic devices having fine patterns. In order to avoid this corrosion, a cleaning process using a cleaning agent containing an organic acid that is less corrosive to tungsten, such as citric acid and oxalic acid, and a chelating agent such as amino polycarboxylic acid has been proposed (Japanese Patent Application Laid-Open No. 10-72594).
In the related art for copper CMP, post-CMP methods typically use acidic cleaning agents containing an organic acid such as citric acid and oxalic acid as a principal component (Japanese Patent Application Laid-Open No. 2001-7071). However, while these cleaning agents have an excellent ability to remove metallic residues, the cleaning agents are highly corrosive to the copper wiring. In order to improve this corrosiveness, alkaline cleaning agents containing an alkanolamine as a principal component are known (Japanese Patent Application Laid-Open No. 11-74243). These cleaning agents have low corrosivity to the copper wiring and have an excellent ability to remove organic residues derived from the anticorrosive added in the CMP slurry. That said, these cleaning agents have a poor ability to remove metallic residues. Alternatively, alkaline cleaning agents having an ability to remove metallic residues are known, said cleaning agents including an organic acid, such as succinic acid and oxalic acid, and an alkanolamine as the principal component (Japanese Unexamined Patent Application Publication No. 2003-536258). However, while these cleaning agents have an excellent ability to remove metallic and organic residues, the cleaning agents are highly corrosive to the copper wiring. Accordingly, such cleaning agents cannot be applied to modern microelectronic devices having fine patterns.